Ascorbic acid is superior to silymarin in the recovery of ethanol-induced inflammatory reactions in hepatocytes of guinea pigs

Both oxidative stress and inflammatory reactions play a major role in alcoholic liver fibrosis. We evaluated the efficacy of ascorbic acid (AA) and silymarin in the regression of alcohol-induced inflammation in hepatocytes of guinea pigs (Cavia porcellus). Animals were administered with ethanol at a daily dose of 4 g/kg body weight (b.wt) for 90 days. On the ninety-first day, ethanol administration was stopped and animals were divided into alcohol abstention group and silymarin- (25 mg/100 g b.wt) and AA- (25 mg/100 g b.wt) supplemented groups and maintained for 30 days. There was a significant increase in the activities of alanine aminotransferase, aspartate aminotransferase, and γ-glutamyl transpeptidase in the serum of the ethanol group. The intracellular reactive oxygen species (ROS) and expressions of cytochrome P4502E1 and nuclear factor κB1, tumor necrosis factor-α, and transforming growth factor-β₁ in hepatocytes were significantly increased in ethanol group. The fibrotic markers α-smooth muscle actin and α ₁(I) collagen and activity of cytotoxicity marker caspase-3 were significantly increased and AA content was significantly reduced in hepatocytes of alcohol-treated guinea pigs. But the AA and silymarin supplementation significantly reduced these changes in comparison with alcohol abstention group. AA could induce greater reduction of inflammatory and fibrotic markers in hepatocytes than silymarin. This indicates that AA is superior to silymarin in inhibiting intracellular ROS generation and thereby reducing the ethanol-induced inflammation in hepatocytes.     

Short-term Effects of Ethanol Intoxication on Ascorbic Acid and Lipid Metabolism and on Drug-metabolizing Enzymes in Liver of Rats

The effects of one-time ethanol intoxication on ascorbic acid and lipid metabolism and on drug-metabolizing enzymes in liver of rats were investigated. Male Donryu rats that had been fed semi-purified feed were given 5 g/kg ethanol solution (25%, w/v) via a stomach tube and killed 16 h after intubation. The amount of ascorbic acid excreted in the urine after ethanol administration increased, but renal and adrenal concentrations of ascorbic acid decreased. The serum levels of total cholesterol, high-density-lipoprotein cholesterol, triglycerides, phospholipids, and non-esterified fatty acids were elevated in rats given ethanol, but hepatic level of total lipids, cholesterol, triglycerides, phospholipids were not. The hepatic concentrations of cytochrome P-450 and cytochrome b₅ did not increase, but this large dose of ethanol increased the activities of aminopyrine N-demethylase and cytochrome c reductase.

These results indicated that the single dose of ethanol affected the ascorbic acid and lipid metabolism of rats, and induced drug-metabolizing enzymes in their liver.     

Protective effects of ascorbic acid, Dl-α-tocopherol acetate, and sodium selenate on ethanol-induced gastric mucosal injury of rats

In this study, the effect of ascorbic acid (vitamin C), Dl-α-tocopherol acetate (vitamin E), and sodium selenate (selenium) on ethanol-induced gastric mucosal injury in rats was investigated morphologically and biochemically. The gastric mucosal injury was produced by administration of 1 mL of absolute ethanol to each rat. Animals received vitamin C (250 mg/kg), vitamin E (250 mg/kg), and selenium (0.5 mg/kg) for 3 d 1 h prior to the administration of absolute ethanol. In gastric mucosa of rats given ethanol according to control groups, neuronal nitric oxide expression decreased. This immunoreactivity was much lower in the group given ethanol+vitamin C+vitamin E+selenium than the control group and the ethanol-induced group. Scanning electron microscopic evaluation of the ethanol-induced group, when compared to control groups, revealed degenerative changes in gastric mucosa, whereas a good arrangement in surface topography of gastric mucosa in the group given ethanol + vitamin C+vitamin E + selenium was observed. In the group administered ethanol, a reduction of the stomach glutathione (GSH) and serum total protein levels and increases in serum sialic acid, triglycerides, and stomach lipid peroxidation (LPO) levels were observed. Vitamin C+vitamin E+Se administration to alcohol-treated rats significantly increased the serum total protein, triglyceride levels, and stomach GSH levels and significantly lowered the levels of serum sialic acid and stomach LPO compared to untreated alcohol-supplemented rats. As a result of these findings, we can say that the combination of vitamin C, vitamin E, and selenium has a protective effect on ethanol-induced gastric mucosal injury of rats.     

Adenosine 2A Receptor Antagonist Prevented and Reversed Liver Fibrosis in a Mouse Model of Ethanol-Exacerbated Liver Fibrosis

The effect of moderate alcohol consumption on liver fibrosis is not well understood, but evidence suggests that adenosine may play a role in mediating the effects of moderate ethanol on tissue injury. Ethanol increases the concentration of adenosine in the liver. Adenosine 2A receptor (A2AR) activation is known to enhance hepatic stellate cell (HSC) activation and A2AR deficient mice are protected from fibrosis in mice. Making use of a novel mouse model of moderate ethanol consumption in which female C57BL/6J mice were allowed continued access to 2% (vol/vol) ethanol (11% calories) or pair-fed control diets for 2 days, 2 weeks or 5 weeks and superimposed with exposure to CCl₄, we tested the hypothesis that moderate ethanol consumption increases fibrosis in response to carbon tetrachloride (CCl₄) and that treatment of mice with an A2AR antagonist prevents and/or reverses this ethanol-induced increase in liver fibrosis. Neither the expression or activity of CYP2E1, required for bio-activation of CCl₄, nor AST and ALT activity in the plasma were affected by ethanol, indicating that moderate ethanol did not increase the direct hepatotoxicity of CCl₄. However, ethanol feeding enhanced HSC activation and exacerbated liver fibrosis upon exposure to CCl_4. This was associated with an increased sinusoidal angiogenic response in the liver. Treatment with A2AR antagonist both prevented and reversed the ability of ethanol to exacerbate liver fibrosis.

Conclusion

Moderate ethanol consumption exacerbates hepatic fibrosis upon exposure to CCl₄. A2AR antagonism may be a potential pharmaceutical intervention to decrease hepatic fibrosis in response to ethanol.     

The effect of trans-ferulic acid and gamma-oryzanol on ethanol-induced liver injury in C57BL mouse

The effects of the oral administration of trans-ferulic acid and gamma-oryzanol (mixture of steryl ferulates) with ethanol (5.0 g per kg) for 30 days to c57BL mice on ethanol-induced liver injury were investigated. Preventions of ethanol-induced liver injury by trans-ferulic acid and gamma-oryzanol were reflected by markedly decreased serum activities of plasma aspartate aminotransferase, alanine aminotransferase and significant decreases in hepatic lipid hydroperoxide and TBARS levels. Furthermore, the trans-ferulic acid- and gamma-oryzanol-treated mice recovered ethanol-induced decrease in hepatic glutathione level together with enhancing superoxide dismutase activity. These results demonstrate that both trans-ferulic acid and gamma-oryzanol exert a protective action on liver injury induced by chronic ethanol ingestion.     

Ascorbic acid supplementation down-regulates the alcohol induced oxidative stress,hepatic stellate cell activation,cytotoxicity and mRNA levels of selected fibrotic genes in guinea pigs

Both oxidative stress and endotoxins mediated immunological reactions play a major role in the progression of alcoholic hepatic fibrosis. Ascorbic acid has been reported to reduce alcohol-induced toxicity and ascorbic acid levels are reduced in alcoholics. Hence, we investigated the hepatoprotective action of ascorbic acid in the reversal of alcohol-induced hepatic fibrosis in male guinea pigs (n = 36), and it was compared with the animals abstenting from alcohol treatment. In comparison with the alcohol abstention group, there was a reduction in the activities of toxicity markers and levels of lipid and protein peroxidation products, expression of α-SMA, caspase-3 activity and mRNA levels of CYP2E1, TGF-β₁, TNF-α and α₁(I) collagen in liver of the ascorbic acid-supplemented group. The ascorbic acid content in liver was significantly reduced in the alcohol-treated guinea pigs. But it was reversed to normal level in the ascorbic acid-supplemented group. The anti-fibrotic action of ascorbic acid in the rapid regression of alcoholic liver fibrosis may be attributed to decrease in the oxidative stress, hepatic stellate cells activation, cytotoxicity and mRNA expression of fibrotic genes CYP2E1, TGF-β₁, TNF-α and α₁ (I) collagen in hepatic tissues.     

Combined effect of selenium and ascorbic acid on alcohol induced hyperlipidemia in male guinea pigs

Alcoholics usually suffer from malnutrition and are especially deficient in micronutrients like vitamin C, selenium and Zn. In the present study, combined effects of selenium and ascorbic acid on alcohol-induced hyperlipidemia were studied in guinea pigs. Four groups of male guinea pigs were maintained for 45 days as follows: control (1 mg ascorbate (AA)/100 g body mass/day), ethanol (900 mg ethanol/100 g body mass + 1 mg AA/100 g body mass/day), selenium+ascorbic acid [(25 mg AA + 0.05 mg Se)/100 g body mass/day], ethanol+selenium+ascorbic acid [(25 mg AA + 0.05 mg Se + 900 mg ethanol)/100 g body mass/day]. Co-administration of selenium and ascorbic acid along with alcohol reduced the concentration of all lipids, as also evidenced from the decreased activities of hydroxymethylglutaryl-CoA reductase and enhanced activities of plasma lecithin cholesterol acyl transferase and lipoprotein lipase. Concentrations of bile acids were increased. We conclude that the supplementation of Se and ascorbic acid reduced alcohol induced hyperlipidemia, by decreased synthesis and increased catabolism.     

Content of liver and brain ubiquinol-9 and ubiquinol-10 after chronic ethanol intake in rats subjected to two levels of dietary alpha-tocopherol

To assess the effect of chronic ethanol ingestion in the content of the reduced forms of coenzymes Q9 (ubiquinol-9) and Q10 (ubiquinol-10) as a factor contributing to oxidative stress in liver and brain, male Wistar rats were fed ad libitum a basal diet containing either 10 or 2.5 mg alpha-tocopherol/100 g diet (controls), or the same basal diet plus a 32% ethanol-25% sucrose solution. After three months treatment, ethanol chronically-treated rats showed identical growth rates to the isocalorically pair-fed controls, irrespectively of alpha-tocopherol dietary level. Lowering dietary alpha-tocopherol led to a decreased content of this vitamin in the liver and brain of control rats, without changes in that of ubiquinol-9, and increased levels of hepatic ubiquinol-10 and total glutathione (tGSH), accompanied by a decrease in brain tGSH. At the two levels of dietary alpha-tocopherol, ethanol treatment significantly decreased the content of hepatic alpha-tocopherol and ubiquinols 9 and 10. This effect was significantly greater at 10 mg alpha-tocopherol/100 g diet than at 2.5, whereas those of tGSH were significantly elevated by 43% and 9%, respectively. Chronic ethanol intake did not alter the content of brain alpha-tocopherol and tGSH, whereas those of ubiquinol-9 were significantly lowered by 20% and 14% in rats subjected to 10 and 2.5 mg alpha-tocopherol/100 g diet, respectively. It is concluded that chronic ethanol intake at two levels of dietary alpha-tocopherol induces a depletion of hepatic alpha-tocopherol and ubiquinols 9 and 10, thus contributing to ethanol-induced oxidative stress in the liver tissue. This effect of ethanol is dependent upon the dietary level of alpha-tocopherol, involves a compensatory enhancement in hepatic tGSH availability, and is not observed in the brain tissue, probably due to its limited capacity for ethanol biotransformation and glutathione synthesis.     

(+)-Catechin as antioxidant: mechanisms preventing human plasma oxidation and activity in red wines

We evaluated the antioxidant effect of (+)-catechin (CTCH), in the presence of physiological antioxidant levels of ascorbic acid (AA), alpha-tocopherol (AT) and beta-carotene (BC), in human plasma oxidised with AAPH. Following a five-hour incubation, the formation of lipid oxidation products (TBARS) was almost doubled, and the concentrations of lipid soluble antioxidants were 10 to 30% from the initial levels. In these conditions, AA was consumed within the first hour of incubation. The addition of CTCH prevented AT and BC depletion and TBARS formation, but had no effect on AA consumption. When the kinetics of oxidation were analysed CTCH oxidation preceded lipid soluble antioxidant depletion, but no consumption of CTCH was associated to AA oxidation. Considering that CTCH could contribute to the antioxidant activity of red wine, we first characterised both the antioxidant capacity and CTCH content of several wines. The wines with highest content of CTCH and antioxidant activity were also the most effective in preventing AAPH-mediated oxidation of plasma vitamin E. Results support the idea that CTCH could have a role as a physiological antioxidant in human plasma, and that CTCH of wine could contribute to the antioxidant status of human plasma.     

Combined effect of ascorbic acid and selenium supplementation on alcohol-induced oxidative stress in guinea pigs

Oxidative stress is a key step in the pathogenesis of ethanol associated liver injury. Ethanol administration induces an increase in lipid peroxidation either by enhancing the production of oxygen reactive species or by decreasing the level of endogenous antioxidants. In this present study, four groups of male guinea pigs (Cavia porcellus) were maintained for 45 days as follows: Control group (1 mg ascorbic acid (AA)/100 g body wt./day); Ethanol group (1 mg AA/100 g body wt./day+900 mg ethanol/100 g body wt./day); Selenium+AA group (25 mg AA+0.05 mg sodium selenite/100 g body wt./day); Ethanol+Se+AA group (25 mg AA+0.05 mg sodium selenite/100 g body wt.+900 mg ethanol/100 g body wt./day). Malondialehyde (MDA), hydroperoxides (HP) and conjugated dienes (CD) were significantly increased, while the activities of scavenging enzymes superoxide dismutase (SOD) and catalase were reduced in the alcohol administered groups. Co-administration of Se+AA along with alcohol increased the activities of scavenging enzymes and reduced the lipid peroxidation products level in hepatic tissues of guinea pigs. Activities of glutathione peroxidase (GPX) and glutathione reductase (GR) were enhanced in co-administered group. gamma-Glutamyl transpeptidase (GGT), a marker enzyme of alcohol induced toxicity, was also reduced, as was the glutathione content. This study suggests that the combined effect of Se+AA, provides protection against alcohol-induced oxidative stress as evidenced from the decreased levels of lipid peroxidation products and enhanced activities of scavenging enzymes.     

The role of glycerol-3-phosphate dehydrogenase 1 in the progression of fatty liver after acute ethanol administration in mice

Acute ethanol consumption leads to the accumulation of triglycerides (TGs) in hepatocytes. The increase in lipogenesis and reduction of fatty acid oxidation are implicated as the mechanisms underlying ethanol-induced hepatic TG accumulation. Although glycerol-3-phosphate (Gro3P), formed by glycerol kinase (GYK) or glycerol-3-phosphate dehydrogenase 1 (GPD1), is also required for TG synthesis, the roles of GYK and GPD1 have been the subject of some debate. In this study, we examine (1) the expression of genes involved in Gro3P production in the liver of C57BL/6J mice in the context of hepatic TG accumulation after acute ethanol intake, and (2) the role of GPD1 in the progression of ethanol-induced fatty liver using GPD1 null mice. As a result, in C57BL/6J mice, ethanol-induced hepatic TG accumulation began within 2 h and was 1.7-fold greater than that observed in the control group after 6 h. The up-regulation of GPD1 began 2 h after administering ethanol, and significantly increased 6 h later with the concomitant escalation in the glycolytic gene expression. The incorporation of ¹⁴C-labelled glucose into TG glycerol moieties increased during the same period. On the other hand, in GPD1 null mice carrying normal GYK activity, no significant increase in hepatic TG level was observed after acute ethanol intake. In conclusion, GPD1 and glycolytic gene expression is up-regulated by ethanol, and GPD1-mediated incorporation of glucose into TG glycerol moieties together with increased lipogenesis, is suggested to play an important role in ethanol-induced hepatic TG accumulation.     

Cytochrome P450 2E1 potentiates ethanol induction of hypoxia and HIF-1α in vivo

Ethanol induces hypoxia and elevates HIF-1α in the liver. CYP2E1 plays a role in the mechanisms by which ethanol generates oxidative stress, fatty liver, and liver injury. This study evaluated whether CYP2E1 contributes to ethanol-induced hypoxia and activation of HIF-1α in vivo and whether HIF-1α protects against or promotes CYP2E1-dependent toxicity in vitro. Wild-type (WT), CYP2E1-knock-in (KI), and CYP2E1 knockout (KO) mice were fed ethanol chronically; pair-fed controls received isocaloric dextrose. Ethanol produced liver injury in the KI mice to a much greater extent than in the WT and KO mice. Protein levels of HIF-1α and downstream targets of HIF-1α activation were elevated in the ethanol-fed KI mice compared to the WT and KO mice. Levels of HIF prolyl hydroxylase 2, which promotes HIF-1α degradation, were decreased in the ethanol-fed KI mice in association with the increases in HIF-1α. Hypoxia occurred in the ethanol-fed CYP2E1 KI mice as shown by an increased area of staining using the hypoxia-specific marker pimonidazole. Hypoxia was lower in the ethanol-fed WT mice and lowest in the ethanol-fed KO mice and all the dextrose-fed mice. In situ double staining showed that pimonidazole and CYP2E1 were colocalized to the same area of injury in the hepatic centrilobule. Increased protein levels of HIF-1α were also found after acute ethanol treatment of KI mice. Treatment of HepG2 E47 cells, which express CYP2E1, with ethanol plus arachidonic acid (AA) or ethanol plus buthionine sulfoximine (BSO), which depletes glutathione, caused loss of cell viability to a greater extent than in HepG2 C34 cells, which do not express CYP2E1. These treatments elevated protein levels of HIF-1α to a greater extent in E47 cells than in C34 cells. 2-Methoxyestradiol, an inhibitor of HIF-1α, blunted the toxic effects of ethanol plus AA and ethanol plus BSO in the E47 cells in association with inhibition of HIF-1α. The HIF-1α inhibitor also blocked the elevated oxidative stress produced by ethanol/AA or ethanol/BSO in the E47 cells. These results suggest that CYP2E1 plays a role in ethanol-induced hypoxia, oxidative stress, and activation of HIF-1α and that HIF-1α contributes to CYP2E1-dependent ethanol-induced toxicity. Blocking HIF-1α activation and actions may have therapeutic implications for protection against ethanol/CYP2E1-induced oxidative stress, steatosis, and liver injury.     

Arjunolic acid,a triterpenoid saponin,prevents acetaminophen (APAP)-induced liver and hepatocyte injury via the inhibition of APAP bioactivation and JNK-mediated mitochondrial protection

Acetaminophen (APAP) is a widely used analgesic and antipyretic drug and is safe at therapeutic doses but its overdose frequently causes liver injury. In earlier studies, we demonstrated that arjunolic acid (AA) has a protective effect against chemically induced hepatotoxicity. The purpose of this study was to explore whether AA plays any protective role against APAP-induced acute hepatotoxicity and, if so, what molecular pathways it utilizes for the mechanism of its protective action. Exposure of rats to a hepatotoxic dose of acetaminophen (700 mg/kg, ip) altered a number of biomarkers (related to hepatic oxidative stress), increased reactive oxygen species production, reduced cellular adenosine triphosphate level, and induced necrotic cell death. Arjunolic acid pretreatment (80 mg/kg, orally), on the other hand, afforded significant protection against liver injury. Arjunolic acid also prevented acetaminophen-induced hepatic glutathione depletion and APAP metabolite formation although arjunolic acid itself did not affect hepatic glutathione levels. The results suggest that this preventive action of arjunolic acid is due to the metabolic inhibition of specific forms of cytochrome P450 that activate acetaminophen to N-acetyl-p-benzoquinone imine. In addition, administration of arjunolic acid 4 h after acetaminophen intoxication reduced acetaminophen-induced JNK and downstream Bcl-2 and Bcl-xL phosphorylation, thus protecting against mitochondrial permeabilization, loss of mitochondrial membrane potential, and cytochrome c release. In conclusion, the data suggest that arjunolic acid affords protection against acetaminophen-induced hepatotoxicity through inhibition of P450-mediated APAP bioactivation and inhibition of JNK-mediated activation of mitochondrial permeabilization.     

Protective effects of ascorbic acid, dl-α-tocopherol acetate, and sodium selenate on ethanol-induced liver damage of rats

In this study, the effect of a combination of vitamin C (ascorbic acid), vitamin E (dl-α-tocopherol acetate), and selenium (sodium selenate) on ethanol-induced liver damage in rats was investigated, morphologically and biochemically. The ethanol-induced injury was produced by the administration of 1 mL of absolute ethanol to each rat. Animals received vitamin C (250 mg/kg), vitamin E (250 mg/kg), and selenium (0.5 mg/kg) (ViCESe) for 3 d 1 h prior to the administration of absolute ethanol. In the liver of the animals given ethanol, the degenerative changes such as extreme hyperemia, vacuolization in cells of portal areas, a dilation in sinusoids, mononuclear cell infiltration, a swelling in cisternae of granular endoplasmic reticulum and in mitochondrial cristae, an increase in smooth endoplasmic reticulum, many lipid vacuoles were observed both light and electron microscopically. A similar structure was usually distinguished when compared with control animals, in rats given ethanol+ViCESe. In this group, the findings indicating cellular damage were either not observed at all or were decreased. In the group administered ethanol, a reduction of the blood glutathione (GSH) level and increases in serum values of alanine aminotranserase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and γ-glutamyl transferase (GGT) activities were observed, whereas in the control group, the reverse was found to occur. On the other hand, in the group in which ethanol+ViCESe was administered, it was observed that the blood GSH value and serum ALP and ALT activities increased and serum AST, LDH, and GGT activities decreased. As a result, the present study indicates that ViCESe because of their antioxidant activity against ethanol damage have a protective effect on the liver.     

Green tea flavonoids inhibit the LDL oxidation in osteogenic disordered rats fed a marginal ascorbic acid in diet

Osteogenic Disorder Shionogi (ODS) rats can not synthesize ascorbic acid (AA). We have examined the capacity of green tea flavonoids (GTF) to modify low-density lipoprotein (LDL) oxidation in ODS rats with dietary AA restriction. In the first experiment, ODS rats were fed diets containing 300 (AA300 diet) or 0 (AA0 diet) mg AA/kg diets for 20 d. In comparison with the AA300 diet, the AA0 diet significantly decreased the concentrations of plasma AA and alpha-tocopherol in LDL and significantly shortened the lag time of LDL oxidation in vitro. In the second experiment, ODS rats were fed one of the following three diets: the AA300 diet, the diet containing 25 mg AA (AA25, marginal AA)/kg diet (AA25 diet), or the diet containing 25 mg AA + 8 g GTF/kg diet (AA25 + GTF diet) for 20 d. Plasma AA concentration were significantly lower in rats fed AA25 compared with AA300 but not in those fed AA25 + GTF. LDL oxidation lag time was significantly longer in rats fed AA25 + GTF compared with the other two groups. Lag time for LDL oxidation was significantly and positively correlated with LDL alpha-tocopherol (r = 0.6885, P = 0.0191). These results suggest that dietary flavonoids suppress the LDL oxidation through the sparing effect on LDL alpha-tocopherol and/or plasma AA when AA intake is marginal in the ODS rats.     

Alcoholic liver disease in rats fed ethanol as part of oral or intragastric low-carbohydrate liquid diets

The intragastric administration of ethanol as part of a low-carbohydrate diet results in alcohol hepatotoxicity. We aimed to investigate whether comparable liver injury can be achieved by oral diet intake. Male Sprague-Dawley rats were fed ethanol as part of low-carbohydrate diets for 36-42 days either intragastrically or orally. Liver pathology, blood ethanol concentration, serum alanine amino transferase (ALT), endotoxin level, hepatic CYP2E1 induction, and cytokine profiles were assessed. Both oral and intragastric low-carbohydrate ethanol diets resulted in marked steatosis with additional inflammation and necrosis accompanied by significantly increased serum ALT, high levels of CYP2E1 expression, and production of auto-antibodies against malondialdehyde and hydroxyethyl free radical protein adducts. However, cytokine profiles differed substantially between the groups, with significantly lower mRNA expression of the anti-inflammatory cytokine interleukin 4 observed in rats fed low-carbohydrate diets orally. Inflammation and necrosis were significantly greater in rats receiving low-carbohydrate alcohol diets intragastrically than orally. This was associated with a significant increase in liver tumor necrosis factor alpha and interleukin 1beta gene expression in the intragastric model. Thus, oral low-carbohydrate diets produce more ethanol-induced liver pathology than oral high-carbohydrate diets, but hepatotoxicity is more severe when a low-carbohydrate diet plus ethanol is infused intragastrically and is accompanied by significant increases in levels of proinflammatory cytokines.     

Stimulation of hepatic phosphatidate phosphohydrolase activity by a single dose of ethanol;.

An acute ethanol load (5 g per kg body wt) given by gastric intubation to fasted rats caused a significant increase in phosphatidate phosphohydrolase activity in the soluble fraction of the liver. The activity was two-fold at 8 hours and three-fold at 16 hours after the ethanol administration and decreased to the control level a few hours after the disappearance of ethanol from the blood. Results from in vivo experiments with intraportally injected [³H]glycerol showed an ethanol-induced cross-over point between glycerol incorporation into phosphatidic acid and neutral glycerolipids. This cross-over could be observed only when the phosphatidate phosphohydrolase activity was increased.     

In vivo assessment of precursor induced prostaglandin release within the rat gastric lumen

Gastroprotection associated with the intragastric administration of prostaglandin (PG) precursor fatty acids such as linoleic (LA), gamma-linolenic (GLA), and arachidionic acid (AA) has been reported to be mediated via their conversion to PGs. This report examines the relationship between gastroprotection and the extent/rate of PG-release in rats intragastrically administered PG biosynthetic precursors: LA, AA, dihomo-gamma-linolenic acid (DHGL) or oleic acid (OA, a nonprecursor fatty acid). At various times following intragastic administration of a fatty acid, gastric fluid was collected, extracted, chromatographed, and assayed for PGE₁ or PGE₂ by specific radioimmunoassay. AA and DHGL dose dependently elevated gastric PGE₂ and PGE₁ levels, respectively. Maximal PGE elevation, 200–400 ng/stomach, was over 400-fold above basal values, and observed within 5–10 minutes of administration. Conversely, OA and LA elicited only a minor (2–10 fold) stimulation of PGE release. In contrast to effects on PG release, all four fatty acids protected the gastric mucosa against macroscopic damage induced by ethanol. The apparent rank order of potency was AA > DHGL = LA > OA (the difference in potency between DHGL or LA and OA was not significant). Since LA and OA (a nonprecursor) only marginally elevated lumenal PGs relative to DHGL or AA, yet were equally efficacious in the gastroprotection assay, it is likely the other fatty acid-related mechanisms play an important role in protecting the stomach against ethanol-induced injury.     

The effects of ascorbic acid deficiency and repletion on pulmonary, renal, and hepatic drug metabolism in the guinea pig.

The effects of ascorbic acid (AA) deficiency on microsomal and soluble (postmicrosomal supernatant) enzymes which catalyze drug metabolism were studied in the guinea pig liver, lung, and kidney, (i) Twenty-one days of AA depletion produced a 50–60% decrease in hepatic cytochrome P-450 levels, 20–30% decreases in renal levels, but no significant changes in pulmonary cytochrome P-450 content. Upon repletion of ascorbic acid, recovery to control levels occurred within 7 days. (ii) The decreases in hepatic cytochrome P-450 in scurvy were not accompanied by a corresponding increase in cytochrome P-420. (iii) Aminopyrine N-demethylation decreased by 40% in livers of deficient animals, and recovered within 3 days, but there were no corresponding changes in lungs and kidneys. (iv) There were no significant alterations of NADPH-cytochrome c reductase activity in scorbutic animals in any of the three organs. (v) Activity of “native” UDP-glucuronyl transferase was increased in liver microsomes after 21 days of deficiency, but this apparent increase was not observed when the enzyme was fully activated in vitro with UDP N-acetylglucosamine. “Native” UDP-glucuronyl transferase was increased in kidneys of deficient animals and unchanged in lungs. (vi) In the postmicrosomal supernatant, glutathione S-aryl transferase activity in deficient livers decreased tc 50% of control and did not fully recover after 14 days of ascorbic acid repletion. These changes were not seen in kidney and lung. (vii) Also in the postmicrosomal supernatant, p-aminobenzoic acid (PABA) N-acetyl transferase activity increased in the kidneys of deficient animals, but was unchanged in liver and lungs. (viii) Addition of ascorbic acid in vitro to hepatic microsomes prepared from scorbutic animals had no effect on activities of aminopyrine N-demethylase, NADPH-cytochrome c reductase, PABA N-acetyl transferase, and glutathione S-aryl transferase.     

Blockade of ethanol induced conditioned taste aversion by 3-amino-1,2,4-triazole: evidence for catalase mediated synthesis of acetaldehyde in rat brain

This investigation seeks to present evidence for the oxidation of ethanol in the brain via the peroxidatic activity of catalase and simultaneously provide evidence for the role of central acetaldehyde (ACH) in the mediation of an ethanol-induced conditioned taste aversion (CTA). Ethanol is capable of inducing a conditioned taste aversion. Pretreatment with the catalase inhibitor, 3-amino-1,2,4-triazole (AT), shows an attenuation of this ethanol-induced CTA. Animals receiving ethanol injections showed a CTA to a novel solution paired with a drug administration, while ethanol injected animals pretreated with AT did not show a CTA to ethanol administration. This effect of AT appears to be specific to the effects of ethanol as CTA's to morphine and lithium chloride were not affected by AT pretreatment. Peripheral levels of ethanol were the same in all animals regardless of pretreatment indicating that AT had no effect on peripheral levels of ethanol. These data increase support for the notion that acetaldehyde is produced directly in the brain and that it may be the agent mediating some of the psychopharmacological properties of ethanol.